I know there is no off/on switch on the KB37 midi controller, and whenever my computer is on, it stays on, unless I was to unplug the usb cable every time I was done. This seems like a pain to have to do that all the time.

Is it bad for it in any way to leave it on all the time. Our computer is only ever turned off at night.

It's USB powered. It's SUPPOSED to be on all the time when the computer is on. It draws no more power than the computer is already using. If you want to turn it off, unplug the USB cable. It doesn't harm the unit, it was designed to run that way. The worst that can happen is eventually a light might burn out. By the time that happens, it's time to get a new keyboard controller anyway.

The information above may not be current, and you should direct questions to the current forum or review the manual.